Highly Selective Artificial K⁺ Channels: An Example of Selectivity-Induced Transmembrane Potential

Abstract

Natural KcsA K+ channels conduct at high rates with an extraordinary selectivity for K+ cations, excluding the Na+ or other cations. Biomimetic artificial channels have been designed in order to mimick the ionic activity of KcSA channels, but simple artificial systems presenting high K+/Na+ selectivity are rare. Here we report an artificial ion channel of H-bonded hexyl-benzoureido-15-crown-5-ether, where K+ cations are highly preferred to Na+ cations. The K+-channel conductance is interpreted as arising in the formation of oligomeric highly cooperative channels, resulting in the cation-induced membrane polarization and enhanced transport rates without or under pH-active gradient. These channels are selectively responsive to the presence of K+ cations, even in the presence of a large excess of Na+. From the conceptual point of view, these channels express a synergistic adaptive behavior: the addition of the K+ cation drives the selection and the construction of constitutional polarized ion channels toward the selective conduction of the K+ cation that promotes their generation in the first place.